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RISS 인기검색어
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- 저자 : Basran, Jaswir (검색결과 2 건)
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Badyal, Sandip K.,Basran, Jaswir,Bhanji, Nina,Kim, Ju Hwan,Chavda, Alap P.,Jung, Hyun Suk,Craig, Roger,Elliott, Paul R.,Irvine, Andrew F.,Barsukov, Igor L.,Kriajevska, Marina,Bagshaw, Clive R. Elsevier 2011 Journal of molecular biology Vol.405 No.4
<P>The interaction between the calcium-binding protein S100A4 and the C-terminal fragments of nonmuscle myosin heavy chain IIA has been studied by equilibrium and kinetic methods. Using site-directed mutants, we conclude that Ca<SUP>2+</SUP> binds to the EF2 domain of S100A4 with micromolar affinity and that the <I>K</I><SUB>d</SUB> value for Ca<SUP>2+</SUP> is reduced by several orders of magnitude in the presence of myosin target fragments. The reduction in <I>K</I><SUB>d</SUB> results from a reduced dissociation rate constant (from 16 s<SUP>− 1</SUP> to 0.3 s<SUP>− 1</SUP> in the presence of coiled-coil fragments) and an increased association rate constant. Using peptide competition assays and NMR spectroscopy, we conclude that the minimal binding site on myosin heavy chain IIA corresponds to A1907-G1938; therefore, the site extends beyond the end of the coiled-coil region of myosin. Electron microscopy and turbidity assays were used to assess myosin fragment filament disassembly by S100A4. The latter assay demonstrated that S100A4 binds to the filaments and actively promotes disassembly rather than just binding to the myosin monomer and displacing the equilibrium. Quantitative modelling of these <I>in vitro</I> data suggests that S100A4 concentrations in the micromolar region could disassemble myosin filaments even at resting levels of cytoplasmic [Ca<SUP>2+</SUP>]. However, for Ca<SUP>2+</SUP> transients to be effective in further promoting dissociation, the elevated Ca<SUP>2+</SUP> signal must persist for tens of seconds. Fluorescence recovery after photobleaching of A431/SIP1 cells expressing green fluorescent protein–myosin IIA, immobilised on fibronectin micropatterns to control stress fibre location, yielded a recovery time constant of around 20 s, consistent with <I>in vitro</I> data.</P>
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Elliott, Paul ,R.,Irvine, Andrew ,F.,Jung, Hyun ,Suk,Tozawa, Kaeko,Pastok, Martyna ,W.,Picone, Remigio,Badyal, Sandip ,K.,Basran, Jaswir,Rudland, Philip ,S.,Barraclough, Roger Cell Press 2012 Structure Vol.20 No.4
<P><B>Summary</B></P><P>Filament assembly of nonmuscle myosin IIA (NMIIA) is selectively regulated by the small Ca<SUP>2+</SUP>-binding protein, S100A4, which causes enhanced cell migration and metastasis in certain cancers. Our NMR structure shows that an S100A4 dimer binds to a single myosin heavy chain in an asymmetrical configuration. NMIIA in the complex forms a continuous helix that stretches across the surface of S100A4 and engages the Ca<SUP>2+</SUP>-dependent binding sites of each subunit in the dimer. Synergy between these sites leads to a very tight association (K<SUB>D</SUB> ∼1 nM) that is unique in the S100 family. Single-residue mutations that remove this synergy weaken binding and ameliorate the effects of S100A4 on NMIIA filament assembly and cell spreading in A431 human epithelial carcinoma cells. We propose a model for NMIIA filament disassembly by S100A4 in which initial binding to the unstructured NMIIA tail initiates unzipping of the coiled coil and disruption of filament packing.</P>
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